JP2808977B2 - Charged particle accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle accelerator for guiding charged particles to a high-frequency electric field to accelerate the charged particles and to increase the kinetic energy.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show a conventional radio-frequency quadrupole.
rupole (RFQ) is a diagram conceptually showing the configuration of a linear accelerator. In the figure, (1) is an accelerating cavity, and (2) to (5) are electrodes, which are arranged at equal intervals radially from the center in the accelerating cavity (1) in a cross section of the accelerating cavity (1). , (2)
Is a first electrode, (3) is a second electrode, (4) is a third electrode, and (5) is a fourth electrode. (6) is a beam inlet provided on one end face of the accelerating cavity (1) for introducing charged particles, and (7) is a beam provided on the other end face of the accelerating cavity (1) for deriving charged particles. The exit, (8) is the beam axis for guiding charged particles, assumed between the beam entrance (6) and the beam exit (7), (9) is the first electrode (2) in the accelerating cavity (1), The second electrode (3), the third electrode (4), and formed between the fourth electrode (5), the beam entrance (6),
This is a vacuum space maintained in a vacuum together with the beam exit (7) and the beam axis (8).

The conventional charged particle accelerator is constructed as described above. When a high frequency corresponding to a predetermined resonance frequency is introduced into the acceleration cavity (1), the first electrode (2) and the second electrode (3) are turned on. ), The third electrode (4), and near the beam axis (8) surrounded by the fourth electrode (5), based on a known principle, an electric field for accelerating the charged particles, and a beam entrance (6). A quadrupole electric field is formed which guides the introduced charged particles to the beam exit (7) with as little loss as possible.

[0004]

The function of the accelerating electric field and the quadrupole electric field in the charged particle accelerator is based on the first electrode.
(2) It depends on the wavy shape of the tip of the second electrode (3), the third electrode (4), and the fourth electrode (5) and the potential of those electrodes.
Here, a quadrupole electric field is concerned, which will be described in detail below. That is, as is known, the quadrupole electric field is
It has the effect of converging or diverging charged particles, and enables transport of charged particles with less loss by combining convergence and divergence. This quadrupole electric field is, for example, the first electrode (2)
And the third electrode (4) at the same positive potential, the second electrode (3) and the fourth electrode
(5) is obtained when the same potential is kept negative, or when the respective electrodes are at the opposite potential. That is, when a strong action is required, it is necessary to increase the potential difference.
However, the distance between the electrodes is limited, the potential difference cannot be increased beyond the dielectric breakdown potential difference between the electrodes, and the intensity of the convergence or divergence of the charged particles is also limited by this.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and the convergence of a radio frequency quadrupole linear accelerator, which is limited by the limitation of a potential difference generated between electrodes, or It is an object of the present invention to obtain a charged particle accelerator in which the divergent action is improved by adding a magnetic field generating coil.

[0006]

A charged particle accelerator according to the present invention generates a magnetic field in a beam axis direction coaxially with a beam axis of a radio frequency quadrupole linear accelerator. A magnetic field generating coil for preventing beam loss is provided based on the above. The magnetic field generating coil arranged according to the present invention is a cylindrical magnetic field generating coil which is excited by a direct current or an alternating current, and is arranged so that its central axis coincides with the beam axis. Also, donut-shaped ring
Shape the quadripolar electric field with the longitudinal sides of each electrode
Penetrating and arranged at right angles to the length, to electrodes facing each other
Fixed and adjacent to the electrode facing each other
The electrode is formed with a gap to penetrate the length of the electrode
Donut-shaped magnets generating locally different magnetic field strengths along the sea
A field generating coil is provided.

[0007]

In the charged particle accelerator configured as described above, the magnetic field generating coil forms a magnetic field only in the beam axis direction near the beam axis, and the charged particles having a component deviating from the beam axis are formed by a known principle. Moves back to the beam axis. Therefore, selection of an appropriate magnetic field strength can help prevent beam loss. In addition, the donut-shaped magnetic field generating coil is composed of a plurality of coil units, each of which generates a different magnetic field strength from each other, and can respond to the magnetic field strength when a locally different magnetic field strength is required. .

[0008]

[Embodiment 1] 1 to 3 show an embodiment of the present invention, in which a radio-frequency quadruple pole (Radio-frequency quadrupole) is shown.
FIG. 2 is a diagram conceptually showing the configuration of a cy Quadrupole (abbreviated as RFQ) linear accelerator. In the figure, (1) is an accelerating cavity, (2)
To (5) are electrodes, which are arranged at equal intervals radially from the center in the acceleration cavity (1) in the cross section of the acceleration cavity (1), (2) is the first electrode, and (3) is the Two electrodes, (4) is the third electrode,
(5) is a fourth electrode. (6) is a beam inlet provided on one end face of the accelerating cavity (1) for introducing charged particles, and (7) is a beam provided on the other end face of the accelerating cavity (1) for deriving charged particles. Exit, (8) is beam entrance (6) and beam exit
Assumed during (7), the beam axis guiding the charged particles, (9) is the first electrode (2), the second electrode (3), the third electrode (4) in the accelerating cavity (1), And a vacuum space formed between the fourth electrode (5) and the vacuum with the beam inlet (6), the beam outlet (7), and the beam axis (8). Reference numeral (10) denotes a known solenoid coil-shaped magnetic field generating coil, which is provided so as to surround the outer periphery of the acceleration cavity (1), and has a symmetric axis and a beam axis of the coil.
(8) is arranged coaxially as much as possible.
(13) is a donut-shaped magnetic field generating coil, the first electrode (2) and
These are fixed to the coil fixing part (11) of the third electrode (4).
The two electrodes (3) and the fourth electrode are electrically insulated from both electrodes.
Connect the coil penetration portion (12) of the electrode (5) to the periphery of the coil penetration portion (12).
And a gap is formed between them so as to penetrate them.

In the charged particle accelerator configured as described above, the solenoid coil-shaped magnetic field generating coil (10) generates a magnetic field in the direction of the beam axis (8) as is well known. When there is a motion component of the charged particle in the direction perpendicular to the beam axis, the motion component generates an action of locating the charged particle in the magnetic field in the beam axis direction, and the action appears as a function of converging the charged particle. . Thus, the radio-frequency quadrupole linear accelerator has a coaxial magnetic field generating coil.
By arranging (10), the divergence action of the space charge of the charged particles can be suppressed, and a high-intensity charged particle accelerator can be realized.

In addition, the charged particle processing device constructed as described above is used.
In the speed control device, the first electrode (2) and the third electrode (4) have the same potential.
Therefore, the above-described configuration is possible. Also, the second electrode
(3) and the fourth electrode (5) have the same potential, but the first electrode (2) and
And the third electrode (4) is different from the second electrode (3) and the fourth electrode (5).
The potential of the second electrode (3) and the fourth electrode (5).
To form an air gap and penetrate the coil penetration part (12)
Insulated. In addition, a donut-shaped magnetic field generating coil (1
The magnetic field generated by 3) is intermittent along the length of the electrode,
The donut-shaped magnetic field is generated by the coil (13)
Placed or sparsely placed. And each
These donut-shaped magnetic field generating coils (13) have different magnetic fields.
Generates strength and requires locally different magnetic field strength
In that case, it can respond to the magnetic field strength.

[0011]

According to the present invention, as described above, the magnetic field generating coil is provided coaxially with the beam axis of the radio frequency quadrupole linear accelerator. Thereby, the divergence of the space charge of the charged particles can be suppressed, and a high-intensity charged particle accelerator can be realized. Also, the donut-shaped magnetic field generating coil is
And fixed to the coil fixing part of the third electrode.
The electrode is electrically insulated from the second electrode and the fourth electrode.
Form a gap between the coil penetrating part and the peripheral
Is placed. This allows for locally different variations along the length of the electrode.
Effect that can respond to the demand for generating magnetic field strength
There is.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part conceptually showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged perspective view showing opposing portions of a first electrode, a second electrode, a third electrode, and a fourth electrode near a beam axis of the acceleration cavity of FIG . 1 ;

FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional charged particle accelerator.

FIG. 5 is a sectional view taken along line BB of FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Acceleration cavity 2 First electrode 3 Second electrode 4 Third electrode 8 Beam axis 10 Magnetic field generating coil 13 Donut-shaped magnetic field generating coil

Claims (1)

(57) [Claims] 1. A radio-frequency quadrupole linear accelerator for forming a quadrupole electric field by high frequency and accelerating charged particles by the high-frequency electric field, wherein the linear accelerator is provided in an accelerating cavity of the accelerator and has a beam axis of the accelerating cavity. A coaxial magnetic field generating coil and a donut-shaped annular part
Penetrate the longitudinal sides of each electrode forming the quadrupole field
Through the above is arranged perpendicular to the longitudinal direction, and oppose each other
Fixed to the electrode and adjacent to the opposite electrode
It is equipped with a gap formed in the other electrode
A source that produces locally different magnetic field strengths along the length of the electrode
A charged particle accelerator comprising a toroidal magnetic field generating coil .